The connection between abnormal protein phosphorylation and the cause or consequence of diseases has been known for over 20 years. Accordingly, protein kinases have become a very important group of drug targets. See Cohen, Nature, 1:309-315 (2002). Various protein kinase inhibitors have been used clinically in the treatment of a wide variety of diseases, such as cancer and chronic inflammatory diseases, including diabetes and stroke. See Cohen, Eur. J. Biochem., 268:5001-5010 (2001).
The protein kinases are a large and diverse family of enzymes that catalyze protein phosphorylation and play a critical role in cellular signaling. Protein kinases may exert positive or negative regulatory effects, depending upon their target protein. Protein kinases are involved in specific signaling pathways which regulate cell functions such as, but not limited to, metabolism, cell cycle progression, cell adhesion, vascular function, apoptosis, and angiogenesis. Malfunctions of cellular signaling have been associated with many diseases, the most characterized of which include cancer and diabetes. The regulation of signal transduction by cytokines and the association of signal molecules with protooncogenes and tumor suppressor genes have been well documented. Similarly, the connection between diabetes and related conditions, and deregulated levels of protein kinases, has been demonstrated. See e.g., Sridhar et al. Pharmaceutical Research, 17(11):1345-1353 (2000). Viral infections and the conditions related thereto have also been associated with the regulation of protein kinases. Park et al. Cell 101 (7): 777-787 (2000).
Protein kinases can be divided into broad groups based upon the identity of the amino acid(s) that they target (serine/threonine, tyrosine, lysine, and histidine). For example, tyrosine kinases include receptor tyrosine kinases (RTKs), such as growth factors and non-receptor tyrosine kinases, such as the src kinase family. There are also dual-specific protein kinases that target both tyrosine and serine/threonine, such as cyclin dependent kinases (CDKs) and mitogen-activated protein kinases (MAPKs).
Protein kinase C (PKC) is a family of serine/threonine kinases that play a pivotal role in cellular signal transduction. Irie et al., 2005, The Chemical Record 5:185-195. PKC isozymes are involved in tumor promotion, as well as other diverse biological events and, accordingly, are attractive targets for cancer therapy and other disorders. Id. One such PKC isozyme which is activated by tumor promoters is PKCθ. PKC isozymes are also expressed in epithelial cells of the gastrointestinal tract, especially the intestine. Farhadi et al., 2006, J. Pharm. Exp. Ther. 316:1-7. Accordingly, agents which modulate PCK activity are thought to be useful as therapeutics for gastrointestinal disorders such as cancer and inflammatory bowel disease.
mTOR (mammalian target of rapamycin), which is also called FRAP, RAFTI or SEPT), is a 2549-amino acid Ser/Thr protein kinase, which has been shown to be one of the most critical proteins in the PI3K/Akt pathway that regulates cell growth and proliferation. Georgakis and Younes, 2006, Expert Rev. Anticancer Ther. 6(1):131-140. Because PI3K and Akt are involved in the regulation of several cellular functions, there may be toxicities associated with inhibiting these kinases, making inhibition of mTOR the more promising approach. Id. Three mTOR inhibitors are currently in clinical trials for the treatment of cancer. These are CCI-779 (renal cancer, breast cancer, mantle cell lymphoma, glioblastoma multiforme and metastatic melanoma), RAD001 (refractory solid tumors, advanced hematologic tumors, GIST and advanced non-small cell lung cancer) and AP23573 (solid tumors, hematologic malignancy and sarcoma). Id. The pre-clinical success of these compounds demonstrates the usefulness of mTOR inhibitors in the treatment of cancer and the need for additional compounds with mTOR inhibitory activity.
Because protein kinases regulate nearly every cellular process, including metabolism, cell proliferation, cell differentiation, and cell survival, they are attractive targets for therapeutic intervention for various disease states. For example, cell-cycle control and angiogenesis, in which protein kinases play a pivotal role are cellular processes associated with numerous disease conditions such as but not limited to cancer, inflammatory diseases, abnormal angiogenesis and diseases related thereto, atherosclerosis, macular degeneration, diabetes, obesity, and pain.
Protein kinases have become attractive targets for the treatment of cancers. Fabbro et al., Pharmacology & Therapeutics 93:79-98 (2002). It has been proposed that the involvement of protein kinases in the development of human malignancies may occur by: (1) genomic rearrangements (e.g., BCR-ABL in chronic myelogenous leukemia), (2) mutations leading to constitutively active kinase activity, such as acute myelogenous leukemia and gastrointestinal tumors, (3) deregulation of kinase activity by activation of oncogenes or loss of tumor suppressor functions, such as in cancers with oncogenic RAS, (4) deregulation of kinase activity by over-expression, as in the case of EGFR and (5) ectopic expression of growth factors that can contribute to the development and maintenance of the neoplastic phenotype. Fabbro et al., Pharmacology & Therapeutics 93:79-98 (2002).
The elucidation of the intricacy of protein kinase pathways and the complexity of the relationship and interaction among and between the various protein kinases and kinase pathways highlights the importance of developing pharmaceutical agents capable of acting as protein kinase modulators, regulators or inhibitors that have beneficial activity on multiple kinases or multiple kinase pathways. Accordingly, there remains a need for new kinase modulators.
Citation or identification of any reference in Section 2 of this application is not to be construed as an admission that the reference is prior art to the present application.